(1,2,4-triazolyl)borate Ligands - WWW-Hosting

C. Janiak, T. G. Scharmann, H. Hemling, D. Lentz, J. Pickardt
235
Transition-Metal Complexes with the Novel Poly(1,2,4-triazolyl)borate Ligands
[HnB(C2H2N3)4- n]- (n = 1 and 2): Synthesis and Characterization of Metal
Complexes of Dihydrobis(1,2,4-triazolyl)borate as One- or Two-Dimensional
Coordination Polymers with Six-Membered Ring Water Substructures and the
Structure of Two-Dimensional Liquid and Solid Water As Organized in the
Intercalate [Ni(HB(C2H2N3)3)2] 6 H 2 0 (X-ray Studies at 293 and 160 K)"
Christoph Janiak"', Tobias G. Scharmann', Holger Hemling', Dieter Lentzb, and Joachim Pickardt'
Institut fur Anorganische und Analytische Chemie, Technische Universitat Berlin",
StraDe des 17. Juni 135, 10623 Berlin, Germany
[nstitut fur Anorganische und Analytische Chemie, Freie Universitat Berlinb,
FabeckstraDe 34-36, 14195 Berlin, Germany
Received September 20, 1994
Key Words : Poly(triazolyl)borates, metal complexes of / Coordination polymers / Water, cluster model /
Water, two-dimensional structure I Hydrogen bonding
The 1:2 manganese ( 5 ) , nickel (6), and copper complex (7)
with the novel dihydrobis(l,2,4-triazolyl)borateligand (2)
were synthesized and structurally characterized. Single-crystal X-ray studies reveal the formation of highly solvated
coordination polymers of the formula [ [M(HZO),(p
. n HzOJ, for M = Mn and Cu. In 5 (M =
HzB(C2H2N3)z]2]
Mn; n = 4) a two-dimensional metal-ligand framework is
built by means of the bridging action of 2. These metal-ligand grid sheets sandwich water layers which comprise individual six-membered rings. Compound 7 (M = Cu; n = 6)
can be described as a linear metal-ligand chain with two borate ligands bridging two copper centers. These one-dimensional coordination polymers are separated by one-dimensional arrays of water molecules in the form of edge-sharing sixmembered rings. In both structures the water of crystallization is held in place both by hydrogen bonding from the aqua
ligands and by hydrogen bonding to the nitrogen atoms of
the borate ligand. Bis[hydrotris(1,2,4-triazolyl)borato]nickel,
[Ni(HB(C2H2N3)3)2]
( 8 ) ,was obtained from NiC12 and the po-
tassium salt of [HB(C2H2N3)J (1). Single-crystal X-ray
structures of the solvate 8 . 6 HzO were determined at 293
and 160 K. The water molecules are arranged in two-dimensional layers with only weak (hydrogen bonding) interactions
to the adjacent layers of the complex molecules. The room
temperature structure (orthorhombic, space group Cmca)
shows a highly disordered water structure being indicative
of a dynamic equilibrium between small conglomerates and
free molecules. Upon cooling an ordering occurs in the water
layer leading to a phase transition in the crystal, and in the
low-temperature structure at 160 K (orthorhombic, space
group Pmnb) the hydrogen atoms and bonding network of
the water structure could be determined. This structure is
best described as being composed of individual rings or
chain segments. The material surface morphology after loss
of the water of crystallization was studied by scanning electron microscopy and the structural pattern correlated with
the crystal packing.
We have engaged in studies of the coordination chemistry
of the potentially ambidentate poly(triazoly1)- and -(tetrazo1yl)borate anions [HB(C2H2N3)3][H2B(C2H2N3)2]-(2), and [H2B(CHN4)J (3)[135,61.These systems can be viewed as modifications of the thoroughly investigated
chelating
poly(pyruzolyE)borate
ligands
[ H B ( ~ z ) ~ ]and
- [HZB(p~)Z](pz = pyrazolyl)[']. The ligand
1 has been found to function mainly as a tris-chelate by
coordination through the endodentate nitrogen donors[' -3,81, whereas in the transition-metal complexes of 3
the formation of 2-D coordination polymers has been the
sole structural motif observed so far[5,61.While the tridentate chelating action of 1 is analogous to [ H B ( ~ z ) ~ ]and
may seem straight-foward, an AM1 theoretical calculation
actually assigns a higher electrostatic potential and negative
charge (-0.19 versus -0.11) to the exodentate N nucleophile~['3~1.
Although these exodentate donors play a part in
the crystal packing by hydrogen bonding to solvent molecules of crystallization, they have only been observed once
in a metal coordination: A case of linkage isomerism in the
zinc
has revealed the formation of the molecular
chelate complex and a three-dimensional coordination
polymer, the latter being built up by the borate 1 bridging
three zinc centers by the exodentate nitrogen atoms. The
reaction conditions for the crystallization of the coordination polymer suggest this allotrope to be the thermodynamically more stable modification in accordance with
the theoretical calculation and posed the question if the
normally observed ready formation of chelate complexes of
1 should be explained by a combination of chelate and ki-
Chem. Ber 1995,128,235-244
0 VCH VerlagsgesellschaftmbH, D-69451 Weinheim, 1995
0009-2940/95/0303-0235 $10.00+.25/0
236
C. Janiak, T. G. Scharmann, H. Hemling, D. Lentz, J. Pickardt
netic effectsL31. For a better understanding of the effects influencing the coordination mode of 1 we have, thus, synthesized the dihydrobis( 1,2,4-triazolyl)borate ligand 2 and
transition-metal complexes thereof.
1
2
two mol of H2 and formation of 4 as a white solid [Eq. (l)].
The dihydrobis(triazoly1)borate anion (2) in the form of
its potassium salt (4) reacts with manganese(I1) and nickel(11) chloride or copper(I1) sulfate in water with the formation of diaquabis[p-dihydrobis(triazolyl)borato]metal(II)
complexes [Eq. (2)]. Upon slow diffusion of solutions of the
Furthermore, the crystal phases of transition-metal com- reactants the manganese compound 5, together with water
plexes with the novel multidentate poly(azoly1)borate li- of crystallization, is obtained as colorless crystals directly
gands l[lp3],3L61, and as we will see here 2, are often stabi- from the reaction mixture in low yield while the nickel and
lized by solvent molecules. Those nitrogen donor atoms in copper compound precipitate initially only as an amorph1-3 which are not utilized for metal coordination can inter- ous blue-violet or dark blue powder under the same conact with the solvent molecules such as water or methanol ditions. The nickel and copper compound are, however, solby hydrogen bonding and carry over some of the solvent- uble in aqueous ammonia (presumably with formation of
solute interaction to the solid state upon crystallization. In ammine-metal complexes) from which they crystallize upon
the tris(triazoly1)borate complexes [M (HB(C2H2N3)3}2]. 6 slow solvent evaporation as violet needles (6) or blue plateH 2 0 with M = Fe, CO, Zn[1,31and [ C U ( H B ( C ~ H ~ N ~ ) lets
~ } ~(7).
] We believe that there is an equilibrium between the
ammine
and the azolyl complex which is shifted during con. 4 CH30H[21and in the bis(tetrazoly1)borate compounds
centration
and evaporation of ammonia to the latter.
{[M(H20>2Cp-H2B(CHN,)2}21.2
H 2 0 1 m (M = Mn, Fe, CO,
X-ray
structural
investigations show that the crystals of
Zn, and Cd) two of the solvent molecules in each case are
5
contain
four,
those
of 7 six molecules of hydrogen-bonded
hydrogen-bonded to nitrogen atomsL6].
water
of
crystallization
per formula unit. The crystals of
The fundamental importance of water drives a quest for
5-7
more
or
less
quickly
eliminate the incorporated solvent
a detailed understanding of the intermolecular forces and
of
crystallization
when
taken
out of the aqueous phase. Exdynamics of the hydrogen bonding networks that operate in
cept
for
the
solubility
of
6
and
7 in aqueous ammonia, the
the condensed phases of waterC91. Hydration together with
bis(triazoly1)borato
transition-metal
complexes are insolhydrogen bonding is not just crucial and has been intensively investigated in biological processes[”] but is impor- uble in water or organic solvents once they have formed.
Aside from the loss of water of crystallization the comtant in inorganic systems as well[”].
In the case of [M{HB(C2H,N3)3)2] . 6 H20 the water pounds are thermally stable to over 200°C. The infrared
substructure presents itself as a two-dimensional layer with spectra reflect the ligand moiety. The quality of the nickel
very weak interactions to the adjacent layers of complex crystals 6 did not allow the collection of a crystallographic
molecules. For a better understanding of this 2-D water data set, however, from a comparison with the IR spectra
structural feature and its hydrogen bonding network we of 5 and 7 we suggest a structure similar to the manganese
have performed a comparative structural study of the nickel compound 5.
Temperature-variable magnetic measurements of 5 and 7
complex [Ni{HB(C2H2N3)3}2]. 6 H 2 0 (8 . 6 H20)at two
show a Curie-Weiss behavior of normal paramagnets in the
different temperatures.
temperature range measured (14-310 K). There is no magnetic coupling transmitted through the ligand, nor is there
Syntheses and Properties of K[H2B(C2H2N3)2](4) and
a through-space interaction of the metal centers (shortest
([M(H20)2(p-H2B(C2H2N3)2)21
n H20), with M = Mn
M-M contacts are 8.14 and 8.92 for 5 and 8.84 or 9.27
(5, n = 4), Ni (6), and Cu (7, n = 6 )
for 7).The magnetic moments are temperature-independent
According to the general synthesis of poly(azoly1)bo- within experimental error and lie within the range typically
rate^[^,'^], potassium boranate (KBHJ reacts with 1,2,4- observed for d5 (high-spin, p = 5.7-6.0 pLg) or d9 comtriazole in a 1:2 mixture at about 125°C with evolution of plexes (p = 1.8-2.1 pS)[l31.
-
A
Chem. Ber. 1995, 128, 235-244
237
Metal Complexes of Dihydrobis( 1,2,4-triazolyl)borate
Synthesis and Properties of [Ni(HB(CzH2N3)3fz]
* 6 HzO
(8 6 HzO)and I N ~ { H B ( C ~ H ~ N ~(8)
)~)ZI
The hydrotris( 1,2,4-triazolyl)borate anion 1 in the form
of its potassium salt reacts with nickel(I1) chloride in water
with the formation of bis[hydrotris(triazolyl)borato]nickel(11) 8 [Eq. (3)]. Upon slow diffusion of solutions of the reactants the complex together with solvent of crystallization
is obtained as red-violet crystals directly from the reaction
mixture in 60% yield.
-
NiCll
+ 2 K[HB(C2H2N3)3]+ [Ni{HB(C2H2N3)3}2]+ 2 KCl
bis@yrazolyl)borate ligand but similar to the dihydrobis(tetruzolyl)borate ligand 3, the dihydrobis(triazoZyl)borate system 2 does not form chelates but generates bridges between
metal atoms. Selected bond lengths and angles for 5 and 7
are collected in Table 1. The B-N, C-N, and N-N bond
length and angle variations are as seen before in the metal
structures of 1[2,31.
Figure 1. View from above a metal-complex layer of 5 (PLUTONplot[4]). The solvate water has been omitted for clarity
(3)
8
An X-ray structural investigation shows that the crystals
of 8 contain six molecules of water per formula unit. Since
the incorporated solvent is quickly eliminated when the
crystals are taken out of the aqueous phase, the resulting
surface morphology was studied by scanning electron microscopy (see below). Complex 8 is only very sparingly soluble in polar solvents such as water, methanol, dichloromethane, or chloroform and insoluble in nonpolar organic
solvents like toluene or hexane.
Compound 8 is thermally stable to above 260°C (melting
or decomposition point undetermined). In the mass spectrum the molecular ion is the base peak. The most likely
fragmentation is loss of two triazolyl moieties and a hydrogen atom to give the second most abundant peak. Another
prominent peak is due to loss of the hydrotris(triazo1yl)borate radical leading to the mono(1igand)metal cation. Fragmentations of the molecular ion, MLZ', and ML+ are very
similar to other tris(triazoly1)metal complexes[*] involving
loss of one or two triazolyl rings together with H, 2 H, and/
or HCN.
A temperature-variable magnetic measurement of 8
shows the expected Curie-Weiss behavior over the temperature range measured. The magnetic moment (p = 3.0 pB at
300 K) is temperature-independent within experimental error and lies within the range typicaliy observed for nickel
complexes (p = 2.9-3.9 pB, calculated spin-only value p =
2.83 pB)"31.
Figure 2. Metal-ligand chain in 7 with the atomic numbering scheme
(50% probability ellipsoids, PLATON-TME plot['4])
b
Figure 3. Metal coordination and atomic numbering scheme in the
manganese complex 5 (PLATON-TME plot['4])
X-Ray Structure of 5 and 7
Compounds 5 and 7 represent themselves as two- or onedimensional coordination polymers, respectively. The arrangement of the metal centers and ligands within the layer
structure of 5 is illustrated in Figure 1, for the linear, "columnane"-type chain[ls1 of 7 in Figure 2. The metal coordination in 5 together with the atom numbering scheme is
detailed in Figure 3. The metal centers in both the manganese and copper complex are octahedrally coordinated,
with the coordination polyhedron being formed from four
nitrogen atoms of the bis(triazoly1)borate ligands and two
truns-coordinated aqua ligands. The Jahn-Teller distortion
in the d9-Cu complex 7 manifests itself in an elongation of
the Cu-OH2 bonds (cf. Table 1). Only the exodentate nitrogen atoms of 2 function as donor atoms to the metal centers
in 5 and 7, in agreement with the charge distribution resulting from an AM1 calculation on the poly(triazoly1)borate ligands['a3I. Thus, in contrast to the bidentate dihydroChem. Ber 1995, 128, 235-244
The coordination mode of 2 towards the metal centers
supports the AM 1-based relative order of the charge densities for the nitrogen donor atoms. To return to the starting
point of our investigations: It appears to be the tris-chelating action in 1 that can successfully compete with the more
thermodynamically favored exodentate coordination, while
the bis-dentate chelate effect in 2 is no longer strong enough
to overcome the charge-dictated ligating requirements.
A further important aspect in the discussion of the crystal structures of 5 and 7 is the stabilization of the crystal
238
C. Janiak, T. G. Scharmann, H. Hemling, D. Lentz, J. Pickardt
Table 1. Selected bond distances [A] and angles
5 [a1
[“I for 5 and 7
7 [bl
Figure 5. Packing diagram of the crystal structure of 7 illustrating the
tubulation of water columns inbetween and arallel to the metal ligand
chains (PLUTON[’’])
n , .
Mn-01
Mn-N6b
Mn-N3
N6-Mn.d
B-N1
B-N4
Nl-C2
Nl-N2
N2-C1
C1-N3
-~~ N3-C2
N4-C4
N4-N5
N5-C3
C3-N6
N6-C4
2.183(3)
2.234(2)
2.265(3)
2.234(2)
1.562(5)
1.574(4)
1.3 18(4)
1.377(4)
1.33114)
0-Mn-N
88.1(1)-91.9(1)
1.323(4)
1.343(4)
1.334(4)
trans 0 - M n - 0 180
tram N-Mn-N 180
87.9(1), 92.1(1)
cis N-Mn-N
105.8(3)
Nl-B-N4
cu-01
Cu-N6b
CU-N~
N6-CU.~
B-N1
B-N4
N 1-C2
N1-N2
N2-C1
C1-N3
N3-C2
N4-C4
N4-N5
N5-C3
C3-N6
N6-C4
2.396(7)
2.016(6)
2.014(7)
2.016(6)
1.585{14)
1.55(2)
1.318( 12)
1.369(11)
1.281(13)
1.340(13)
1.3OO(12)
1.310(12)
1.372(11)
1.291(12)
1.35i(i2j
1.317(12)
0-CU-N
86.8(4)-94.2(4)
178.5(4)
177.1(4)
89.9(4)-90.1(2)
108.6(8)
trans 0-Cu-0
tram N-Cu-N
cis N-Cu-N
Nl-B-N4
Symmetry transformations used to generate equivalent atoms: b =
+ 112, y + 112, -Z + 312; d = -X + 112, y - 112, -Z + 312. Eb] Symmetry transformations used to generate equivalent atoms: b =
-X f 112, y, z - 112.
X , -y + 312, z f 112; d
--x
phase by solvent molecules as has been observed already in
metal structures of the other novel poly(azoly1)borates 1
and 3[1-3,61.The nitrogen donor atoms in 1-3 which are
not utilized for metal coordination can interact with the
solvate molecules such as water (or in one case methanol)
by hydrogen bonding and carry over some of the solventsolute interaction to the solid state upon crystallization. In
2, water molecules are hydrogen-bonded to both endodentate nitrogen atoms. As a consequence the metal complex
layers in 5 are separated by layers of water molecules
(alternatively, the metal complex grid sheets sandwich the
water layer) and so are the metal-ligand columns in 7. A
stereoview and a packing diagram of the crystal structures
in Figures 4 and 5, respectively, illustrate the layer- and
channel-type inclusion phenomena[l6I in 5 and 7, respectively, which can also be described as clathrates[171.
The quality of the room-temperature data set of 5 allowed the determination of the hydrogen bonding network
around the water molecules. Their hydrogen atoms were lo-
M
cu
O N
.C
Q O
O B
O H
cated and their positions refined. The potential hydrogen
bond lengths and angles of the short intermolecular contacts are given in Table 2. Figure 6 presents a view of the
water layer from above, including the hydrogen-bonded nitrogen atoms of the triazolyl rings (shaded circles). The
water layer in 5 is built up by separate rings comprised of
six oxygen atoms in a chair conformation with heterodromic[l81hydrogen-bonded circles. Each of the water species is threefold coordinated (when including the nitrogen
and metal acceptors), and the water of crystallization donates one H bond to the “surface”, i.e. to a nitrogen atom,
of either one of the neighboring metal-ligand layers.
In the water substructure of 7 most, but not all, hydrogen
atoms could be located with certainty. Therefore, only the
O.-O contacts of the potential hydrogen bonds are shown
in Figure 7. A list of these short contacts is included in
Table 2. The water structure in 7 is built up from rings of
six oxygen atoms sharing opposite edges, reminiscent of a
band or ladder polymer such as polyacene. Water aggregates as rings comprised of five or six 0 atoms are formed
preferentially for topological reasons. The O...O distances
shown in the water substructures of Figures 6 and 7 lie
within the normal range of 2.6 to 3.0 A[18].The H...O/N
contacts in Figure 6 between 1.81 and 2.13 are considerably shorter than the sum of the van der Waals radii of 2.6
for H and 0 or 2.7 for H and N[’91.
A
Figure 4. Stereoview of the crystal structure of 5 illustrating the intercalation of a water layer between the metal ligand grid sheets (PLUTON[l4I)
Chem. Ber. 1995, 128,235-244
Metal Complexes of Dihydrobis(l,2,4-triazolyl)borate
239
Table 2. Hydrogen-bonding schemes in compounds 5 and 7
5 [a1
Donor-H-Acceptor
01-Hl002
01-H11'..03
02-H2O-N2e
02-H21-.03f
03-H31-N5f
D-A
D-H
H-A
[AI
[AI
[AI
2.694(4)
2.847(4)
3.031(5)
2.858(5)
2.796(5)
0.88(5)
0.81(3)
0.92(5)
0.92(5)
0.96(5)
1.81(5)
2.05(4)
2.1315)
1.96(5)
1.85(5)
D-H-A
["I
1736)
167(4)
165(4)
166(5)
173(5)
7P I
Donor(-H)
-Acceptor
D-.A
[A]
Donor(-H)
-Acceptor
D-A
[A]
01-02
01-03
02.-04
02-N5e
03--N2f
2.81( 1)
2.81( 1)
2.78(1)
2.90(1)
2.93(1)
03-03g
04-02
02-02g
03-04h
04.03b
2.79(1)
2.78(1)
2.73(1)
2.75(1)
2.75(1)
Symmetry transformations used to generate equivalent atoms: e =
x, y, z - 1; f = ;x
1, -y
1, -z + 1. - All ojher 0-0 contacts
are above 3.56 A, the 0.-N contacts above 3.29 A. - Cb] Symmetry
312,
transformations used to generate equivalent atoms: b = x, -y
z + 112; e = x 112, -y + 1, -z + 112; f = -x + 1 , y + 112, -z
-t 112; g = - X
312, -y
312, Z; h X ; -Y + 312, z - 112. All other 0-0 contacts are above 3.86 A, the 0-N contacts above
3.31 A.
+
+
+
generates two independent borate ligands. The nickel octahedra are arranged in layers separated by layers of water
molecules. The facile loss of the water when the crystal is
removed from solution indicates, however, rather weak solvent-solute interactions. A stereoview of the crystal structure (Figure 9) illustrates the formation of this intercalateor layer-type clathrate[171.
Figure 7. View of a water chain (oxygen centers only, crossed circles)
in compound 7 with the short intermolecular contacts as dashed lines
and including the hydrogen-bonded nitrogen atoms of the triazolyl
rings as well as the coordinated copper atoms (PLUTON[l4I). The
atomic numbering scheme is illustrated; for symmetry labels see Table 2
+
+
+
Figure 6. View from above of a water layer in compound 5 with the
hydrogen bonding network (dashed lines) and including the hydrogenbonded nitrogen atoms of the triazolyl rings (shaded circles, PLUThe atomic numbering scheme is illustrated; for symmetry
labels see Table 2
b
Figure 8. Molecular structure of [Ni{HB(C2H2N3)3}2]in 8 . 6 H20.
The atomic numbering refers to the room-tem erature structure (50%
probability ellipsoids, PLATON-TME plotcl$); in the isostructural
low-temperature form the borate ligands are no longer symmetry-related
Qo
0
0
N6
6
X-Ray Structure of 8 * 6 H20
The molecular structure of 8 is shown in Figure 8. The
borate ligand functions as a tridentate chelate through the
endodentate nitrogen donors to give octahedrally coordinated nickel. Selected bond distances and angles are compiled in Table 3. There is no change in the nickel coordination polyhedron when going to lower temperature, aside
from a lower crystal symmetry (Pmnb versus Cmca) which
removes the inversion symmetry from the nickel center and
Chem. Ber. 1995, 128, 235-244
"6
The change in temperature leads to an ordering in the
water layer to which we ascribe the phase transition leading
to the difference in space groups. The packing of the oxygen
centers within the layer at the two temperatures is illustrated
in Figure 10. At 293 K all water molecules except for the
N...H -O-H...N-fixed ones (dark circles) are disordered.
This disorder is a manifestation of the high thermal mobility and the dynamic behavior of liquid water. If an O...O
distance in the range of about 2.6 to 3.0 A is assumed for
hydrogen bonding['s], the time-averaged structure of the
two-dimensional aqueous phase has to be described by
small H 2 0 clusters and isolated H 2 0 molecules. Such a description would be consistent with the Nemethy-Scheraga
model discussed for liquid water[20].
A significantly reduced disorder is apparent for the lowtemperature structure (Figure 10 and 11). The quality of
C. Janiak, T. G. Scharmann, H. Hemling, D. Lentz, J. Pickardt
240
Figure 9. Stereoview of the crystal structure of 8 . 6 HzO (low temperature) illustrating the intercalation of a two-dimensional water layer
between metal complex layers (PLUTON plot[141)
Table 3. Selected bond distances [A] and angles
293 and 160 K
T = 293 K Ial
T = 160 K
["I
for complex 8 at
Cb1
Ni-NZ
Ni-N5
B-N1
B-N4
N142
NI-NZ
NZ-CI
Cl-N3
N342
N U 4
N4-NS
N543
C3-N6
N-4
2.087(3)
2.094(2)
1.544(5)
1.542(3)
1.33l(4)
1.376(3)
1.315f4)
1.349(4)
1.325(5)
1.335f3)
1.370(3)
1.318(3)
1.349(4)
1.329(4)
Ni-NZ
Ni-NS
B1-N1
Bl-N4
N142
NI-N2
NZ-Cl
Cl-N3
N342
N U 4
NGN5
N523
CSN6
N U 4
2.071(5)
2.088(3)
1.527(8)
1.547(5)
1.343(7)
1.376(6)
1.303(7)
1.365(8)
1.331(8)
1.3346)
1.37l(4)
1.312(5)
1.349(5)
1.323(5)
warn N-Ni-N
cis N-Ni-N
Nl-B-N4
N4-LN4c
180.0
86.04(9)-93.96(9)
107.6(2)
106.8(3)
rims N-Ni-N
179.4(2)
86.2(1)-94.1(1)
108.2(3)
N7-BZ-NlO
108.8(2)
N10-BZ-N10a
cis N-Ni-N
NI-Bl-N4
N4-Bl-N4a
La] Symmetry operations: c = -x
a = x, -y t 112, z.
+ 1, y, z. - (1'
Ni-N8
Ni-NI 1
BZ-N7
BZ-N10
N746
N7-N8
N&-C5
CS-N9
N946
N10--C8
N10-NI1
N 1 1 4
C7-N12
NI248
107.7(4)
108.3(5)
Symmetry operations:
this low-temperature data set allowed the determination of
the hydrogen bonding network around the water molecules.
The hydrogen atoms of the latter were located and their
positions refined. The potential hydrogen bond lengths and
angles of the short intermolecular contacts are given in
Table 4. Figure 11 presents an on-top view of the water
layer including the hydrogen-bonded nitrogen atoms of the
triazolyl rings (shaded circles). Note the positional disorder
of one hydrogen on 0 2 and the two-site position of 05. At
both temperatures it is evident that two out of the six H20
molecules per formula unit form hydrogen bonds to four
exodentate nitrogen atoms. Even at low temperature, however, the water layer in 8 . 6 H 2 0 is not built up from edgesharing O6 rings (as in ice
which have been
observed in structures with stronger host-guest interactions
such as in Cd(H20)2Ni(CN)4 . (H20)4[22].Rather, the hydrogen-bonding framework of the water molecules appears
to form kinked strands of O8 rings, which run colinear to
the b axis. However, when the split position of the 0 5 atoms
and of the hydrogen atoms on 0 2 is taken into account the
strands are interrupted, and the water structure is better
described as being comprised of individual rings or chain
segments. Then the structure of the water layer (ordered by
rapid cooling of the crystal) resembles more that of a frozen
liquid with a temperature-dependent formation of larger
H20
Figure 10. View from above of a water layer in 8 . 6 HzO at 293 (a)
and 160 K (b). The three crystallographically different oxygen positions are represented differently in a (0 atoms related by disorder are
shown alike as void and crossed circles). In the area of the unit cell in
a all oxygen centers are shown, outside two out of the three respective
disordered positions were removed for a visualization of the possible
HzO clustqing [d ( 0 - 0 ) = 2.54-2.66, - - - d(Q-0) =
2.95-3.02 A, unconnected oxygen centers are more than 3.1 A apart].
To allow a better comparison of the orderidisorder the same representation and unit cell content were also adopted in b, despite the fact that
the different space group at 160 K gives rise to five crystallographically indepented oxygen positions (see Figure 11)
0
0
'1
1
b
Scanning Electron Microscopy
The surface structure of 8 after the loss of water of crystallization from a cubic crystal plate has been studied by
scanning electron microscopy (SEM). The SEM pictures
Chem. Ber. 1995, 128,235-244
24 1
Metal Complexes of Dihydrobis( 1,2,4-triazoIyl)borate
Figure 11. View from above of a water layer in 8 . 6 H 2 0 at 160 K
with the hydrogen-bonding network (dashed lines) and including the
hydrogen-bonded nitrogen atoms of the triazolyl rings (shaded circles,
PLUTON['4]). The atomic numbering scheme is illustrated. 03, 0 1 ,
and 0 2 lie on a mirror plane (symmetry operation x, 0.5 - y, z); for
the symmetry labels, see Table 4
+
Q....__. .-...Q
I
Table 4. Hydrogen-bonding scheme in the low-temperature structure
of 8 . 6 HzOIal
~
Donor-H-Acceptor
Q._._
&.__....
Q
i
01-H1 l...N6b
02-H21**.01
02-H22**.04
03-H3l...N12~
04d-H41d..05
05-H52..01
05-H51...03
D*A
[AI
D-H
H-A
D-H-A
[AI
[AI
["I
2.864(5)
2.874(8)
2.752(.7)
2.860(5)
2.58(1)
2.897(9)
2.878{9)
0.79(4)
0.82(6)
0.86(7)
0.78(4)
0.85(6)
0.96(5)
1.02(5)
2.08(4)
2.06(6)
1.97(9)
2.1 l(5)
1.85(6)
2.20(8)
2.06(8)
177(5)
179(8)
149(10)
161(6)
143(7)
129(5)
135(3)
Symmetry transformations used to generate equivalent atoms: b =
+ 0.5, -y, z - 0.5; c = -x, -y, -2 + 1; d - X , -yo + 1,
-2 + 1. - All other 0-0 and 0-N contacts are above 3.23 A.
[a]
--x
diffusion progressing from the crystal surfaces to the interior.
Conclusions
are displayed and correlated with the crystal morphology
and packing in Figure 12. The rectangular sides of the cubic
plate show fine tears with the same directionality running
parallel to the long edges (Figure 12 a). The square-basal
plane of the plate, however, has the appearance of a cracked
brick wall, "built" in line with the diagonal of the plane
(Figure 12 b). Precession-camera photographs allowed us
to establish a correlation between the crystallographic axes
and the crystal morphology: The longest axis b stands perpendicularly on the square-basal plane or parallel to the
short edges, while the approximately equal a and c axis (cf.
Table 6, room-temperature structure) are positioned along
the plane diagonals or through the short edges of the crystal
plate (see Figure 12). Picturing the unit cell relative to its
position within the cubic plate provides then an understanding of the surface fractures: The water layers run parallel to the ac plane (a) or parallel to the long rectangular
edges, and the metal-complexes are "lined-up" along a and
c in their layers (b). Diffusion of the water out of the crystal
lattice then leaves molecular-sized openings which can, of
course, not be detected with the available magnification, but
an imperfect collapse or closing of the gaps between the
metal complex layers along b leads to the larger, visible
cracks in Figure 12 a, and gives rise to the brick pattern in
b. The latter emerges since the intermolecular interaction
between the complexes is not the same along a and c (at
this point it was not possible to decide which axis, a or c,
corresponded to which diagonal) and since the closure of
the gap between the layers occurs stepwise with the water
Chem. Ber. 1995,128, 235-244
The novel bis(l,2,4-triazolyl)borate ligand 2 exhibits the
expected bridging coordination mode for poly(triazoly1)borates by the exodentate nitrogen atoms and, thereby, illustrates the chelate effect at work in the molecular complexes formed with the tris( 1,2,4-triazolyl)borate ligand 1.
The crystal phases of the metal-bis(triazoly1)boratesystems
are stabilized by water molecules which in turn are organized into an ordered hydrogen-bonded network of isolated or edge-sharing six-membered rings by the template
effect of the endodentate nitrogen atoms and the metalaqua ligands.
The X-ray structure of the solvated octahedral chelate
complex [Ni{HB(C2H2N3)3)2] . 6 H 2 0 shows complex-containing layers sandwiching weakly hydrogen-bonded water
layers. The room-temperature structure, despite the highly
disordered water molecules, supports a cluster-model description for two-dimensional liquid water. At 160 K, these
water molecules organize into a fully ordered hydrogenbonded network. All of the hydrogen atoms could be refined and thus the cluster-like nature of the 2-D water layer
revealed in intricate detail.
This work was supported by the Deutsclie Forschungsgemeinschaft (grant Ja466/4-l), the Fonds der Chemischen Industrie, and
the Freunde der TU Berlin. We express our appreciation and thanks
to Prof. H. Schumann for his generous and encouraging support
and to Mrs. M. Borowski for collecting the crystallographic data set
of 7.The help of Dr. W a n t h e r and (in part) Dr. H. W Sichting
in obtaining the magnetochemical data and the precession-camera
photographs is appreciated. We thank Mr. G Urmann from the
Heinrich-Hertz-Institut fur Nachrichtentechnik Berlin GmbH for the
SEM photographs.
Experimenta1
Bidistilled or de-ionized water was used as a solvent. - CHN:
Perkin-Elmer Series I1 CHNS/O Analyzer 2400. - IR: PerkinElmer 580B or Nicolet Magna 750. - MS: Varian MAT 311A. NMR: Bruker ARX 200. - Susceptibility measurements: Faraday
magnetic balance and AC susceptorneter Lakeshore Model 7000.
- Precession camera: STOE, MO-K, radiation. - SEM: CamScan;
C. Janiak, T. G. Scharmann, H. Hemling, D. Lentz, J. Pickardt
242
Figure 12. Crystal morphology with relative positions of crystal axes and unit cell (room temperature) and SEM surface structures of a dried
cubic crystal plate of 8, (a) viewed from above the rectangular side (parallel to the ac plane) and (b) viewed from above the square basal plane
(along b). In the unit cell a only the oxygen centers (crossed circles) are shown for the water molecules and only the “middle” oxygen center
which occupies a special position is displayed for the disordered H20 molecules (cf. Figure 10). In the view from above a metal-complex layer
in b the water molecules have been omitted for clarity
or
f’-
a
IY------
a/C
30 pm
the dried crystal plate was mounted on the rectangular side and C4H6BKN6 (188.0): calcd. C 25.55, H 3.22, K 20.79, N 44.69;
sprayed
with a 10-15 nm gold layer. - The potassium salt of 1 found C 25.77, H 3.56, K 20.01, N 43.80.
. .
was synthesized from KBH, and triazole according to r e f ~ . [ ~ . ’ ~ ] .
f[Mn(H20)2/~-H2B(C2H2N3)2)2]
4 H20), (5): A solution of
K[H2B(C2H2NJ2] (4): In a 100-ml flask equipped with a gas 0.06 g (0.5 mmol) of anhydrous MnC12 in 10 ml of water was caremeter an intimate mixture of 2.1 g (40 mmol) of KBH4 and 5.9 g fully overlayered in a test tube with a solution of 0.19 g (1.0 mmol)
(85 mmol) of triazole was heated to about 120°C. At this temp. a of 4 in 20 ml of water. Slow diffusion of the solutions of the starting
brisk hydrogen evolution started and in a few minutes about 95% compounds then led to the formation of 5 as colorless crystals.
(= 1.9 I) of the estimated hydrogen was evolved, after which the gas Yield 0.05 g (22%), m.p. 1 260°C. - IR (KBr): 0 = 3403 cm-l s
evolution quickly subsided. A porous soft material was obtained. (br, OH), 3145 vw, 2926 vw, 2854 vw, 2444 m, 2410 m, 2349 w,
The reaction was allowed to continue for some time during which, 2269 w, 1738 vw, 1666 w, 1637 w, 1525 sh, 1514 s, 1432 w, 1342 w
however, only an additional 0.02 1 of hydrogen was collected. After to m, 1283 m, 1272 m, 1180 m, 1148 vs, 1124 s, 1023 m,997 m,
cooling to room temp. the solid was washed three times with 25 ml 990 m, 976 sh, 890 m, 871 w, 723 vw,674 m, 663 w, 627 m. of warm tetrahydrofuran to remove unreacted triazole. Drying in Magnetic moment: p = 5.7 pg (300 K). - CsH24B2MnN1206
vacuo yielded 6.7 g (90%) of a snow-white powder which was used (460.9): calcd. C 20.85, H 5.25, N 36.47; found C 20.30, H 5.04, N
as such for the synthesis of the transition-metal complexes. Analyti- 36.49 (hydrated, crystalline material).
cal samples were recrystallized from methanol or ethanol; m.p.
293-295°C (dec.). - IR (KBr): 0 = 3218 cm-I m, 3205 m, 2435
/ [ M ( H Z ~ ) ~ ( / I - H ~ B ( C ~ .Hn ~HN20)~ ) ~[M
) ~=] Ni, n undem, 2405 m, 2350 m, 2290 w, 2267 w, 1503 s, 1411 w, 1312 m, 1265 termined (6);Cu, n = 6 (7)]: A solution of 1.0 mmol of the trans, 1208 m, 1178 s, 1155 vs, 1128 w, 1121 w, 1028 m, 1021 m, 962 sition-metal salt (0.13 g of NiC12 or 0.25 g of CuSO, . 5 H20) in
w, 884 s, 873 w, 725 w, 685 s, 674 s, 676 w, 658 w, 641 m. - ‘H 10 ml of water was carefully overlayered in a test tube with a soluNMR (D20): 6 = 7.92 (s, 1 H, “C1”-H), 8.26 (s, 1 H, “C2”-H) (BH tion of 0.38 g (2.0 mmol) of the potassium salt of 2 in 20 ml of
signal could not be observed due to its broad resonance because water. No crystalline material, only a blue-violet (6) or dark blue
of quadrupolar coupling and relaxation effects from the boron (7) voluminous amorphous precipitate formed which after filtration
atom[23]).- 13C NMR (DzO): 6 = 149.2 (“C2”), 152.4 (“Cl”). (A was completely dissolved in 3 mI of concentrated aqueous amdirect assignment of the two ‘H- or I3C-NMR signals to the two monia (25%) to afford a clear violet or deep blue solution, respecdifferent hydrogen or carbon atoms was not possible. From a com- tively. Slow solvent evaporation gave lilac needles (6) or dark blue
parison with the thoroughly studied poly@yrazoZyr)borate spec- crystal plates (7). When removed from the water phase the crystals
traLz4I we infer the assignments given above. For the “CI”I”C2”- quickly turned opaque with loss of crystallinity due to the evapotype description cf. the atom numbering in Figures 2 or 3.) - ration of water of crystallization.
Chem. Ber. 1995, 128, 235-244
243
Metal Complexes of Dihydrobis(1,2,4-triazolyl)borate
Compound 6 (dried material): Yield 0.20 g (50'1/0), m.p. >26OoC.
- IR (KBr): 3 = 3360 cm-' m (br, OH), 3185 vw, 2924 vw, 2455
m, 2434 m, 2370 w, 2277 w, 1766 w, 1656 sh, 1622 m, 1505 s, 1436
w, 1420 w, 1317 m, 1284 s, 1235 w, 1189 m, 1155 s, 1137 m, 1042
s, 986 w, 970 w, 962 m, 888 m, 870 m, 723 w, 673 s, 634 vw, 598 w.
- C8HL6BZNl2NiO2
(392.6): calcd. C 24.45, H 4.11, N 42.82; found
C 23.59, H 4.98, N 43.77.
Compound 7 (dried material): Yield 0.10 g (~SYO),m.p.
202-205°C. - IR (KBr): 3 = 3383 cm-' m (br, OH), 3132 m, 2425
m (BH), 2288 w, 1660 w (br), 1520 s, 1443 w, 1333 w, 1285 m, 1185
sh, 1153 s, 1121 s, 1024 m, 1014 m, 1004 m, 876 m, 726 w, 671 s,
650 w. - Magnetic moment: p = 2.0 pg (300 K). C8HI6B2CuNl2O2
(399.3): calcd. C 24.06, H 4.04, N 42.09; found
C 25.75, H 3.45, N 44.05.
[Ni(HB(C2H2N3)z}2]
(8): A solution of 0.23 g (1.0 mmol) of
NiC12 . 6 H 2 0 in 10 ml of water was carefully overlayered in a
test tube with a solution of 0.50 g (2.0 mmol) of K[HB(C2H2N3)3]
(potassium salt of 1) in 20 ml of water. Some amorphous material
precipitated in this process. Upon slow diffusion of the solutions
of the starting compounds the originally light-green nickel chloride
solution turned blue, the upper colorless borate layer became light
pink-violet, and the first red-violet crystals of 8 . 6 H 2 0 started to
form within 24 h. The reaction and process of crystallization were
concluded within 2 weeks to give analytically pure, well-shaped
crystals. Except for the X-ray diffraction studies, the solvent-free
lilac-colored complex obtained upon air-drying of the crystalline
material was analyzed. Yield 0.30 g (6IYo), m.p. >260"C (not determined). - IR (CsI): 3 = 3129 cm-' w, 3100 m, 3089 m (C-H),
3000 vw, 2518 w, 2495 m (B-H), 1507 s, 1415 m, 1328 m, 1322 m,
1291 s, 1229 w, 1218 w, 1202 m, 1193 m, 1150 s, 1102 w, 1049 m,
1029 s, 969 sh, 964 s, 925 w, 905 sh, 894 m, 872 m, 787 w, 730 sh,
719 s, 674 s, 665 sh. - MS (EI, 70 eV, 240"C), mlz (%): 490 (100,
M+'), 422 (35, [M - C2H,NJ+), 420 (14, [M - C2HZN3 - 2H]+),
353 (92, [M - 2 CZH2N3 - HI+), 352 (62, [M - 2 C2H2N3 2H]+'), 326 ( 5 , [M - 2 C2H2N3 - H - HCN]+), 274 (75, [M HB(CZHZN~)~I+=
[ N ~ { H B ( C Z H ~ N ~ ~ ) I219
+),
(24,
[Ni{HB(C2H2N3)3)- 2 HCN - HI+'), 206 (7, [Ni{HB(C2H2N3)3}
- C2H2N,]+'), 205 (7, [Ni{HB(C2H2N3),}- C2H2N3- HI'), 178
(17, [Ni{HB(C2H2N3)3}- C2H2N3 - H - HCN]+), 177 (20,
[Ni{HB(C2HZN3),}- C2HZN3- 2 H - HCN]"), 165 (19, 152
(12, [Ni{HB(C2H2N3)3f- C2H2N3- 2 HCN]+'), 129 (lS), 69 (10,
[C2H3N3]+')(peaks listed refer to the most abundant isotope combination 58Ni, I'B). - Magnetic moment: p = 3.0 pB (300 K). Cl2HI4B2Nl8Ni
(490.7): calcd. C 29.37, H 2.88, N 51.38; found C
29.18, H 2.57, N 51.92.
6 H20. Crystal data are listed in Table 5 for 5 and 7 and in Table
6 for the two temperature forms of 8 . 6 H20[26].
Table 5. Crystal data for compounds 5 and 7
5
Formula
M O ~mass
.
[g mo1-11
Crystal size [mm]
Crystal system
Space group
v [A3]
z
Dc&d. [g cm-3i
F(O00)
~ ( M O K ~[mm-l]
L)
Absorption correction:
max.; min.; av.
Measured reflections
Unique reflections
Data €orrefinement (n)
Parameters refined (p)
4[a]: max;min [e A-31
R I ; wRZ ib] [ I > Za(1)]
Goodness of fit [cl
Weighting scheme, w ;
a; b Id]
==
Chem. Ber. 1995, 128, 235-244
C4H12BMn0.5N603 CSH28B2CuN1208
(C8H24B2MnN1206)
230.48 (460.96)
505.59
1.0. 0.6 0.1
0.5 .0.2 . 0.1
Monoclinic
Orthorhombic
P21h (No. 14)
Pccn (No. 56)
8.140(3)
9.483(2)
15.953(6)
14.080(2)
8.918(4)
17.688(3)
105.95(3)
90.00(2)
1113.4(8)
2361.9(7)
4
4
1.375
1.422
478
1052
0.641
0.962
DIFABS
DIFABS
1.294; 0.716; 0.970 1.002; 0.498; 0.673
2206
1839
1823 mint = 0.0268) 1104 (Rint = 0.1416)
1818
1104
181
193
0.25; -0.26
0.51; -0.56
0.0413; 0.0746
0.0846; 0.1273
0.968
1.208
0.0221; 3.48
o.oO0; 0.O00
La] Largest difference eak and hole. - Ch] R1 = Z 11 F, I - I F, Il)/c
lFol; wR2 = [Z[w
F32]/Z [w~@']]'". - 1' Goof = [Z [ w ( c
2-
- FZ)']/(n - P ) ] ~ -~ Cd1
. w = l/[o (F;)
P = [max(F; or 0) + 2 . Fz]/3.
+ (a
i
. P)2 + b . PI where
Table 6. Crystal data for compound 8 . 6 H20 at 293 and 160 K
Temperature
293 K
Formula
MOLmass [g mol-11
Crystal size [mm]
Crystal system
Space group
C12H26B2N1806Ni
598.82
0.5 .0.5* 0.5
0.2 .0.2 . 0.1
Orthorhombic
C m a (No. 64)
Pmnb (Pnma; No. 62)
10.890(7)
20.769(5)
20.998(13)
10.801(2)
11.754(8)
11.635(3)
2688(3)
2610(1)
4
4
1.480
1.524
1240
0.768
0.791
none
DIFABS
1.234; 0.879; 0.980
1610
2230
1540 (Rint = 0.0176) 2227 (Rint= O.oo00)
1534
2185
138
262
0.33; -0.76
0.38; -0.33
0.0389; 0,0956
0.0553; 0.0902
1.044
1.084
:[AIg;
c
X-Ray Structure Determinations: STOE four-circle diffractometer for 5 [oscan (5" < 2 0 c 50°, -9 c h 9, 0 k S
18, 0 s 1 < 101 and 8 . 6 H 2 0 [ambient temp., 293 K, o scan (4"
c 2 0 < 54", -16 S h < 16, 0 S k < 30, 0 S 1 < 16)]; CAD4,
Enraf-Nonius four-circle diffractometer for 7 [o-20 scan (5" S 2 0
< 55", 0 ih < 11, 0 G k c 16, 0 s I S 21)] and 8 . 6 H20 [low
temperature, 160 K; w-20 scan (2" < 2 0 < 50", 0 < h S 12, 0 c
k
24, 0 S I c 13)]; the crystals of 5, 7, and 8 . 6 H 2 0 were
measured in capillaries at room temp. (293 K), for the low-temperature data collection of 8 . 6 H 2 0 the crystal was taken out of the
aqueous phase and quickly transferred to the cold nitrogen stream
of the diffractometer. MO-K, radiation (h = 71.069 pm, graphite
monochromator). Structure solutions were performed by direct
methods (SHELXS-86rz5I). Refinement: Full-matrix least-squares
(SHELXL-93rz51)with all non-hydrogen atoms anisotropic. The hydrogen atoms were located and refined, except for those in the disordered water molecules of the room-temperature structure of 8 .
7
v[~31
z
D,alcd. [g cm-31
F(O00)
~ ( M O K C[mm-']
~)
Absorption correction:
max.; mm.; av.
Measured reflections
Unique reflections
Data for refinement (n)
Parameters refined (p)
~p [a]: max;min [e A-31
RI; wR2 lb] [I > 2u(I)]
Goodness of fit lcl
Weighting scheme, w ;
a; b Ld]
[a-d]
See Table 5.
0.059; 0.85
160 K
0.010 9.90
C. Janiak, T. G. Scharmann, H. Hemling, D. Lentz, J. Pickardt
244
* Dedicated to Prof. Dr. Hubert Schmidbaur on the occasion of
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Rejnement, Gottingen, 1993; SHELXS-86, Program for Crystal
Structure Solution, Gottingen, 1986.
[261 Further details of the crystal structure determinations are available on request from the Fachinformationszentrum Karlsruhe,
Gesellschaft fur wissenschaftlich-technischeInformation mbH,
D-76344 Eggenstein-Leopoldshafen, on quoting the depository
number CSD-58672, the authors, and the journal citation.
[37 1/94]
[14]
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Chern. Ber. 1995, 128,235-244